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‘Quantum mechanics reveals a mystery at the boundary of physics: that observation strangely influences what is observed. Quantum Enigma focuses on this increasingly discussed skeleton in physics’ closet, its encounter with consciousness.”

Quantum mechanics reveals a mystery at the boundary of physics: that observation strangely influences what is observed. Quantum Enigma focuses on this increasingly discussed skeleton in physics’ closet, its encounter with consciousness.

Does the elimination of the conscious observer imply a mind independent reality?

At a general level, you can't eliminate the conscious observer. We're here thinking about whether "conscious collapse" is relevant to QM, after all - that's part of our mental model of QM, whichever way we decide.

Does the elimination of the conscious observer imply a mind independent reality?

Afraid I have not read the book. If Nauenberg represents what it says accurately though it falls into the same traps a lot of commentators on QM do.

It may be worth mentioning that several of the information or decoherence type interpretations replace an observer as an irreversible flow of information outside the quantum system. This leads to a constrained phase space in the future evolution of the system. This kind of interpretation avoids things like 'observers', 'minds', 'conciousness' and so on that are very poorly defined concepts in physics. Which is probably why it appeals to me as a "Shut up and calculate" kind of physicist.

Afraid I have not read the book. If Nauenberg represents what it says accurately though it falls into the same traps a lot of commentators on QM do.

It may be worth mentioning that several of the information or decoherence type interpretations replace an observer as an irreversible flow of information outside the quantum system. This leads to a constrained phase space in the future evolution of the system. This kind of interpretation avoids things like 'observers', 'minds', 'conciousness' and so on that are very poorly defined concepts in physics. Which is probably why it appeals to me as a "Shut up and calculate" kind of physicist.

Coming from the other side, it has always struck me that (the small number of) physicists who champion "conscious collapse" (like Rosenblum and Kuttner) have a very poor understanding of consciousness as either a neurocognitive or philosophical concept. They just say (in effect), "consciousness does it" and fold their arms as if they've said something coherent.

Coming from the other side, it has always struck me that (the small number of) physicists who champion "conscious collapse" (like Rosenblum and Kuttner) have a very poor understanding of consciousness as either a neurocognitive or philosophical concept. They just say (in effect), "consciousness does it" and fold their arms as if they've said something coherent.

Grant Hutchison

I can well believe that. It is the sort of area of area of inquiry that needs a multidisciplinary approach if you are going to rigorously investigate it, not physicists doing poor philosophy/neuroscience or philosophers/neuroscientists doing poor physics. I'm reminded of the "Conciousness is a quantum effect" debate that went on a decade or so ago and generated a lot of press. As far as I could tell the majority of the physicists who felt able to comment on it authoritatively had an argument that boiled down to "Conciousness is weird. Quantum effects are weird. So Conciousness must be due to Quantum Effects." A little digging threw up a few people from a range of disciplines trying to do genuinely interesting science in the area, but they didn't seem to be the ones giving interviews...

Regardless of the QM variant, the dual split experiment displays a wave interference pattern on the screen, when equipment is not set up to see which slit goes through, even when a single particle at a time is sent, and a particle impact pattern when it is. Regardless of the mathematical explanation, it is the result which counts and it evidences particle - wave duality.

Coming from the other side, it has always struck me that (the small number of) physicists who champion "conscious collapse" (like Rosenblum and Kuttner) have a very poor understanding of consciousness as either a neurocognitive or philosophical concept. They just say (in effect), "consciousness does it" and fold their arms as if they've said something coherent.

Yes, a lot of what is not understood about consciousness in physics has to do with what is not understood about consciousness, rather than not understanding what it means to have a conscious experience of a measurement, or a conscious experience of what information is. So all that is being said is that we have not well unified the process by which the brain acquires information with the equations of physics that refer to said information, but we certainly understand what information is when we see it in physics (we have to, or we are totally unable to do physics). Thus, the issue is not about whether we are talking about consciousness or information, they are not different when it comes to doing physics. That we don't understand how to unify them is annoying, but is not an impediment to using either concept in physics.

A related source of confusion is the difference between an actual observer and a hypothetical one, as you pointed out above. When an experiment is set up that is capable of informing a conscious observer, it makes no difference if there is actually present such an observer. Hence, the consciousness of an observer is not needed to collapse a wavefunction, it is needed to even be able to assert what knowledge is, what data is, what a measurement is, and what collapse is. It is our consciousness that is needed for us to understand what a physics experiment is. That's why people using different interpretations of quantum mechanics say different things happen in an experiment, including the fact that some say collapse to a single outcome never happens at all. You can't have a more obvious role for consciousness in quantum mechanics than that!

Yes, I know. It doesn't add much, beyond special pleading that they meant something completely different from what reviewers and readers were actually taking away from their book. I find I can't critique Kuttner's response (which I find naive) any further without falling foul of Swift's injunction.

In my opinion, the main flaw in the argument is the idea that somehow quantum mechanics is the first time physics has "encountered" consciousness. Actually, physics has always required consciousness, and it has always swept that fact under the rug. Quantum mechanics was the place this was noticed, which is quite different.

As an example of what I mean, what really distinguishes quantum mechanics from other branches of physics is the inclusion of probability as fundamental, not just to the theory, but to the description of reality itself. Statistical mechanics and thermodynamics, with their key notion of entropy, have long been theories of probability, but they were clear that this was how the physics was choosing to treat reality, moreso than what reality "really is." This is obvious-- in classical mechanics, a treatment of what reality "really is" must always have entropy zero, if what is is, since entropy is essentially the natural log of the number of yes/no questions you would need to answer to expand the information you currently have about a system to get to all that "is." More precisely, both quantum mechanics and statistical mechanics approach in precisely the same way systems that are fully decohered, meaning, systems that can be expressed in terms of a diagonal "density matrix" of real numbers that give the probability of the system being in various completely specified states. Quantum mechanics differs only in that the system need not be in a fully decohered state, but different interpretations of quantum mechanics do not differ on the basic mathematics describing systems becoming decohered, they differ on what to make of that final decohered state. And since statistical mechanics uses the exact same final decohered state, all the same questions already existed for statistical mechanics!

I'll give you a simple example-- you flip a coin in the air and slap it to your arm, covering the outcome. Physics will now treat that coin in a fully decohered state (coins are always treated as being in fully decohered states), which is a 50/50 mixed state of heads and tails. So would quantum mechanics, if you were "flipping an electron" instead. No difference! So where is the "encounter" with consciousness? It comes in the same place in both cases-- you are now free to say that the coin (or the electron) is either heads or tails already, and you just don't know which, or you can say it is neither until a conscious observer has checked it. You can even say reality splits into two "worlds," one in which the coin/electron is heads, and one in which it is tails, and your consciousness is merely found to inhabit one or the other when you look (and go through whatever physiological process occurs when you gain some knowledge). That's what demonstrably always happens in physics (or more correctly, this is how we understand and describe what goes on in physics, whenever we are not sweeping this fact under the rug)-- some consciousness undergoes some physiological process that allows them to test some expectation. Could any experiment distinguish those two ways of looking at what happened, perhaps for the coin, but not for the electron? No-- no experiment could possibly distinguish them, in neither context, there simply is no difference whatsoever in how quantum mechanics and statistical mechanics treat mixed states.

So maybe you think the difference is prior to the decoherence, when quantum mechanics allows a state that statistical mechanics does not-- the "superposition state." That is certainly a difference, but here's the problem-- physics tests always deal with mixed states. No one ever tests anything else except mixed-state predictions. Ever. And to be science, it must be testable, so there cannot be a difference in a testable claim about "what is" at any level where quantum mechanics is dealing with different objects than statistical mechanics is. The issues were always exactly the same. Indeed, one could easily claim the first place we "encountered" consciousness was our first brush with classical chaos theory, when Poincare proved 2D dynamical systems are not chaotic (sweeping rather completely under the rug all the higher dimensional systems physics encounters all the time!). Had Poincare intuited that this would be very much the exception rather than the rule for nonlinear dynamical systems, he would have come fully into contact with the need to address consciousness when making claims about the nature of physical systems, decades before quantum mechanics. It's purely an accident of history that quantum mechanics came first.

So why do people think the "encounter" with consciousness happens only in quantum mechanics? It is simply because there is a prevailing interpretation of statistical mechanics, but there is an argument about quantum mechanics. No one thinks the coin is either heads or tails until a consciousness looks at it, because our shared intuition is that the coin is already one or the other when flipped, even when no apparatus is deployed that could determine which it is. Classical mechanics conventionally imagines what amounts to a "universal consciousness," a kind of "answer man" that knows all, even when the information given to the physicist does not. It's the physics before there is physics of the coin, that's the thing we all agree on in classical contexts, but haven't tested because we can't-- any more than we can test it in quantum mechanics. It's just more clear that there is "physics before the physics" in quantum mechanics than it ever was before, because the concept of a "universal consciousness that knows all" runs afoul of the theory prior to when we can test it. Hence the "shut up and calculate" school, which essentially says the physics comes only once there is physics (i.e., once there are measurements to compare with calculations), and not before-- that school applies just as well to mixed states in classical physics. But no one ever really does that-- we all end up imagining some physics before the physics. And in that imagination, we find the role of consciousness.

In the double slit experiment a light source or electron beam gun is
shot at the plate with two slits. If one sets up the experiment to
observe which slit the particles go through result in particle impact
pattern, else a wave interference pattern.

That is not how I would describe it. However, the grammar of your
statements is slightly messed up. That might account for at least
some of the problem. Can you fix the grammar so the statements
say exactly what you meant?

Originally Posted by gzhpcu

Sure Jeff. Could you please point out which statements are not well
expressed and I will try to restate them.

Originally Posted by Strange

I assume Jeff is referring to:

If one sets up the experiment to observe which slit the
particles go through [it] result[s] in [a] particle impact
pattern, else a wave interference pattern.

But it seems pretty unambiguous even without being perfect.
(I hadn't even noticed.)

Originally Posted by gzhpcu

Regardless of the QM variant, the dual slit experiment displays
a wave interference pattern on the screen, when equipment is not
set up to see which slit goes through, even when a single particle
at a time is sent, and a particle impact pattern when it is.

Strange's correction of the grammar short-circuited the effect
I was hoping for. I hoped that gzhpcu would think further about
what he was trying to say, and revise his descriptions of how the
patterns are created. I said, "That is not how I would describe it."
I was hoping gzhpcu would come up on his own with a description
that more clearly explains for him why the patterns are different
that does not involve the light changing in any way. He has the
idea that the light changes from waves into particles, and it would
be most effective if he figures out for himself that it doesn't.

gzhpcu,

It isn't clear to me what you mean by "particle impact pattern".
I think we can say that the light (or electrons) *always* make a
"particle impact pattern", nomatter what the pattern looks like.
As you said, even when a single particle is sent through at a
time, we can get an interference pattern created by the double
slit, and still identify the location of impact of each individual
photon or electron on the screen. In that case, we have no
way of knowing which slit the photon or electron passed
through. It seems to have gone through both.

It isn't clear to me what you mean by "particle impact pattern".
I think we can say that the light (or electrons) *always* make a
"particle impact pattern", nomatter what the pattern looks like.
As you said, even when a single particle is sent through at a
time, we can get an interference pattern created by the double
slit, and still identify the location of impact of each individual
photon or electron on the screen. In that case, we have no
way of knowing which slit the photon or electron passed
through. It seems to have gone through both.

-- Jeff, in Minneapolis

Jeff, by particle impact pattern, I mean the impact pattern you would expect when you shoot bullets through the the two slits. This occurs when a detector observes which slit the particle goes through. If no such detector is in place, then both slits are sources of a wave and the two interfere with each other. The pattern on the wall is one of wave interference and is not a particle (bullet) pattern. Is this clearer?

But if you detect the photon at the slit you then know it's there so you would expect it to be a bullet particle. If you don't detect the photon at the slit you don't know which slit it goes through so it appears like a wave. The detector and the screen are both detection devices. The slit detector forms the physics before the physics of the screen detector, to use KenG 's words.

sicut vis videre estoWhen we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.Originally Posted by Ken G

Thing is, a photon never "appears like a wave". A particle is received at a detector. If we receive enough particles from a double slit experiment, then we find that their reception pattern over time builds up to look like wave interference. But that pattern is built one particle at a time.

Yes thanks, I should have added the statistical nature. I was going to add than even buckyballs c60 have been thrown at two slits and an interference pattern emerges but one ball at a time. The balls do not become waves.

sicut vis videre estoWhen we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.Originally Posted by Ken G

Yes, the thing that "appears like a wave" is what I meant by the "physics before the physics"-- it is how we make sense of the behavior of the particle, but we only ever measure the particle behavior when doing experiments in the quantum limit. We can use tricks like tunneling electron microscopes to use one particle to probe the "wavefunction" of another, but we still only detect the particle, and make sense of the wavefunction. And of course, the particles we ultimately see are photons detected by our optic nerves, or locations of dials we could feel with our hands, which are particle-like objects. So we do a lot of mental manipulation to come up with the concept of a wave, and we are indeed surprised when we find ways of putting in the wave concept where we did not expect to, but that's also where the multiple interpretations come in.

So the difference between getting a wave pattern and a particle pattern on the screen is not really the difference between the particles behaving like waves or not, because they still behave like particles when they hit the screen. The difference is how soon in the process can we understand them like particles, versus at which point it works better to think of them as waves. But personally, I like to think of them in every situation, always, as particles that are told what to do by waves (in the sense that they are particles that follow wave mechanics). They always do that-- even when making a "particle pattern." The "aha" is when you realize that waves can already do everything we think of as "particle-like"-- even trajectories.

Hence, the "wavelike" elements are always all a question of just two aspects-- the waves involved in the superposition of the full "wave behavior," and their wavelengths.
Everything we ever meant about "particlelike motion" always just referred to culling out the superposition such that it limited the degree of coherence between different wave modes, and culled out the longer wavelengths. That's it, that's all you ever need to get particlelike motion-- it was always something waves do, we just didn't notice this until we bumped into quantum mechanics. Kind of like the role of consciousness in physics.

So then, what is the difference when we put in a detector that gives us "which slit" information, why does that give a "particlelike" pattern? It is not changing any waves into particles, it is simply culling the waves that contribute. The information in the system removes the crosstalk between the waves corresponding to going through one slit and the waves corresponding to going through the other, so we get no "both slit-like" behavior, but it's still all things that waves do-- just waves culled in the ways we are used to culling them when we set up experiments. There was never "particlelike motion," it was always particles doing what waves tell them to do, but we just never thought of it that way until we needed to.

Thing is, a photon never "appears like a wave". A particle is received at a detector. If we receive enough particles from a double slit experiment, then we find that their reception pattern over time builds up to look like wave interference. But that pattern is built one particle at a time.

Jeff, by particle impact pattern, I mean the impact pattern you
would expect when you shoot bullets through the two slits. ...
Is this clearer?

Yes, thank you. You used the expression "particle impact pattern"
to refer to the pattern by its cause, while I was trying to interpret
the expression as referring to the pattern by its appearance, which
confused me. Partly because the appearance of the pattern tells
us nothing about the wave properties of the particles unless we
know the configuration of the slots and the source.

The banded interference pattern that results in the double slit
experiment actually is the pattern you get when you shoot bullets
through the slits, although that pattern won't be apparent unless
the bullets and slits are appropriately proportioned to each other.

Thing is, a photon never "appears like a wave". A particle is received at a detector. If we receive enough particles from a double slit experiment, then we find that their reception pattern over time builds up to look like wave interference. But that pattern is built one particle at a time.

Grant Hutchison

I never said it did. i said the impact pattern.

Profloater's was the post I was replying to. We had a little conversation, three posts long, centred on the post of mine you quoted.

And of course particle is the word we use to describe what a particle detector detects, we don't go further into what that Really means. But in detecting particles (my corrector just wrote per tickle which is cute) in that way we can get down to integer numbers 1,2,3 not 1.567. Just like in the oil drop experiment at school we can get down to integer steps in volts applied so we know we have 1,2,3 electrons so we can call electrons particles. No one will ever see an electron in an electron microscope but we know what we mean by particle even if we do not get deeper into a photon than that it excites a photon multiplier and it's a good name.

sicut vis videre estoWhen we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.Originally Posted by Ken G

The banded interference pattern that results in the double slit
experiment actually is the pattern you get when you shoot bullets
through the slits, although that pattern won't be apparent unless
the bullets and slits are appropriately proportioned to each other.

Is that true? How do bullets interfere with one another? (Unless you are going to say that they can be treated just like very massive quantum objects, in which case the analogy become meaningless.)

The slits need to be separated by a distance roughly on the order of the wavelength. The de Broglie wavelength of a sample bullet is about 10-33m, which means the slits have to be closer together, by many orders of magnitude, than the diameter of a proton. So the bullets are going to interact with many, many quantum objects as they attempt to pass through these "slits" - they're therefore going to end up behaving like classical objects, rather than quantum objects.